How to set up ghost

I purchased a domain and attempting to use digital ocean ghost image. This has failed as follows:

? Enter your blog URL: https://blog.johnnyscott.co.uk
✔ Configuring Ghost
✔ Setting up instance
+ sudo useradd --system --user-group ghost
+ sudo chown -R ghost:ghost /var/www/ghost/content
✔ Setting up "ghost" system user
ℹ Setting up "ghost" mysql user [skipped]
+ sudo mv /tmp/blog-johnnyscott-co-uk/blog.johnnyscott.co.uk.conf /etc/nginx/sites-available/blog.johnnyscott.co.uk.conf
+ sudo ln -sf /etc/nginx/sites-available/blog.johnnyscott.co.uk.conf /etc/nginx/sites-enabled/blog.johnnyscott.co.uk.conf
+ sudo nginx -s reload
✔ Setting up Nginx
✖ Setting up SSL
+ sudo mv /tmp/blog-johnnyscott-co-uk/ghost_blog-johnnyscott-co-uk.service /lib/systemd/system/ghost_blog-johnnyscott-co-uk.service
+ sudo systemctl daemon-reload
✔ Setting up Systemd
+ sudo systemctl is-active ghost_blog-johnnyscott-co-uk
+ sudo systemctl start ghost_blog-johnnyscott-co-uk
+ sudo systemctl is-enabled ghost_blog-johnnyscott-co-uk
+ sudo systemctl enable ghost_blog-johnnyscott-co-uk --quiet
✔ Starting Ghost
One or more errors occurred.

1) Setting up SSL

Message: Uh-oh! It looks like your domain isn't set up correctly yet.
Because of this, SSL setup won't work correctly. Once you've set up your domain
and pointed it at this server's IP, try running `ghost setup ssl` again.

Also getting these errors when running suggested solution…

root@ghost-ubuntu-s-1vcpu-1gb-nyc3-01:~# ghost doctor
You can't run commands as the 'root' user.
Switch to your regular user, or create a new user with regular account privileges and use this user to run 'ghost doctor'.
Working directory is not a recognisable Ghost installation.
Run `ghost doctor` again within a folder where Ghost was installed with Ghost-CLI.
ghost-mgr@ghost-ubuntu-s-1vcpu-1gb-nyc3-01:~$ -i -u ghost-mgr
ghost-mgr@ghost-ubuntu-s-1vcpu-1gb-nyc3-01:~$ ghost setup ssl
Working directory is not a recognisable Ghost installation.
Run `ghost setup` again within a folder where Ghost was installed with Ghost-CLI.

Should the blog url be only the domain name or with a prefix like blog that I added ?

Any suggestions please ?